I noticed, when using the TimeInfo plugin with the analog clock bitmap, that the line drawing routine in the SDK is far from ideal; at some slopes, the line is discontinuous. So I browsed around the internet and found a great routine that produces flawless lines (Bresenham's line drawing routine), and it's probably faster than the routine that was implemented in the SDK. I modified it to work in lcdbitmap.h:
Code:
void line(unsigned int X1, unsigned int Y1, unsigned int X2, unsigned int Y2, PixelStyle style)
{
assert(X1 <= m_width-1);
assert(Y1 <= m_height-1);
assert(X2 <= m_width-1);
assert(Y2 <= m_height-1);
// these if's make sure we only use the relatively expensive algorithm if we're drawing a sloping line
if ((Y1 == Y2) && (X1 == X2)) {
setPixel(X1, Y1, style);
}
else if (Y1 == Y2) {
hLine((X1<X2)?X1:X2, Y1, (X1<X2)?X2-X1:X1-X2, style);
}
else if (X1 == X2) {
vLine(X1, (Y1<Y2)?Y1:Y2, (Y1<Y2)?Y2-Y1:Y1-Y2, style);
}
else {
int dy = Y2 - Y1;
int dx = X2 - X1;
int stepx, stepy;
if (dy < 0) { dy = -dy; stepy = -1; } else { stepy = 1; }
if (dx < 0) { dx = -dx; stepx = -1; } else { stepx = 1; }
dy <<= 1; // dy is now 2*dy
dx <<= 1; // dx is now 2*dx
setPixel(X1, Y1, style);
if (dx > dy) {
int fraction = dy - (dx >> 1); // same as 2*dy - dx
while (X1 != X2) {
if (fraction >= 0) {
Y1 += stepy;
fraction -= dx; // same as fraction -= 2*dx
}
X1 += stepx;
fraction += dy; // same as fraction -= 2*dy
setPixel(X1, Y1, style);
}
} else {
int fraction = dx - (dy >> 1);
while (Y1 != Y2) {
if (fraction >= 0) {
X1 += stepx;
fraction -= dy;
}
Y1 += stepy;
fraction += dx;
setPixel(X1, Y1, style);
}
}
}
}
I recompiled the TimeInfo plugin with this new routine and it works brilliantly.
You can download the modified version of lcdbitmap.h
here.
The algorithm I use is almost directly copied from
this page, step 3
-edit-
I ran into a rounding error which caused degreeLine() to draw sloped lines at angles like 90°. Now that's fixed too in this new lcdbitmap.h.
Login
FAQ
Search
